A craft consisting of a gasbag, filled with gas lighter than the surrounding air, from which a basket or instruments can be suspended. Balloons are now used as a means of meteorological, infrared, gamma-ray, and ultraviolet observation.

NASA has developed an Ultra-Long Duration Balloon to circle the Earth at the edge of space. Balloon packages are also used as space probes, for example, by the Soviet Vega mission that placed atmospheric balloons in Venus's atmosphere in 1985.